206541721 has 4 divisors (see below), whose sum is σ = 218691252. Its totient is φ = 194392192.

The previous prime is 206541719. The next prime is 206541737. The reversal of 206541721 is 127145602.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 138297600 + 68244121 = 11760^2 + 8261^2 .

It is a cyclic number.

It is not a de Polignac number, because 206541721 - 2¹ = 206541719 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 206541721.

It is not an unprimeable number, because it can be changed into a prime (206541121) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 6074740 + ... + 6074773.

It is an arithmetic number, because the mean of its divisors is an integer number (54672813).

Almost surely, 2^206541721 is an apocalyptic number.

It is an amenable number.

206541721 is a deficient number, since it is larger than the sum of its proper divisors (12149531).

206541721 is a wasteful number, since it uses less digits than its factorization.

206541721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12149530.

The product of its (nonzero) digits is 3360, while the sum is 28.

The square root of 206541721 is about 14371.5594491343. The cubic root of 206541721 is about 591.1113029663. Note that the first 3 decimals are identical.

The spelling of 206541721 in words is "two hundred six million, five hundred forty-one thousand, seven hundred twenty-one".